Relative Speed / Altitude

STK Premium (Air) or STK Enterprise
You can obtain the necessary licenses for this tutorial by contacting AGI Support at support@agi.com or 1-800-924-7244.

Capabilities Covered

This lesson covers the following STK Capabilities:

  • Aviator Pro

Problem Statement

The Relative Speed / Altitude strategy is a vertical plane strategy in which the aircraft flies to a constant speed and altitude / elevation angle relative to a cooperative aircraft from STK's Aviator capability.

Cooperative Target

Field Description
Cooperative Target

Select an Aviator aircraft in the scenario that the aircraft will follow during the maneuver.
Pos/Vel Strategies

Position and velocity strategies for the target object. The following strategies are available:

  • NoisyBrgRng - A noisy bearing and range strategy.
  • NoisySurfTgtPosVel - A strategy that periodically generates noisy position, speed, and course updates for a constant altitude target.
Tgt Pos/Vel Resolution

The frequency of sampling of the target object's position and velocity; interpolation of the object's position will be performed between sample points.

The lowest recommended value for this property is 0.1 sec, but the lowest possible value is 0.001 sec. At the lowest value, Aviator will use the native position and velocity of the target object; this can result in dramatically slow performance when the target object is another Aviator aircraft, since STK is performing double integration calculations in such a case.

Hold Objective

By default, the aircraft will maneuver to and maintain the specified Altitude Offset from the target. Click the drop-down menu to select a different hold objective:

  • Hold Initial Offset Alt - maintain the altitude at the beginning of the maneuver.
  • Hold Elevation Angle - maneuver to and maintain the specified Elevation Angle (relative to the local horizontal) from the target's perspective.
  • Hold Initial Elevation Angle - maintain a constant elevation angle (relative to the local horizontal) from the target's perspective, determined from the elevation angle at the beginning of the maneuver.

Airspeed Controls

Field Description
Offset Airspeed The difference in airspeed between the aircraft and the target, until the Range to Transition Speed is satisfied.
Use Target Aspect for Airspeed If selected, the airspeed difference between the aircraft and the target will be computed by Aviator, based on the target aspect; this enables the aircraft to decelerate in a situation where it is actually ahead of the target.
Use Performance Model Limits  
Range for Equal Speed The range at which the aircraft will achieve the same airspeed as the target.
Range to Transition Speed The range at which the aircraft will begin to slow down to match the speed of the target.

Altitude and Airspeed Boundaries

The Min Altitude, Max Altitude, Min Airspeed, and Max Airspeed fields define absolute airspeed and altitude boundaries for the maneuver.

Stop Condition

Select a stopping condition from the drop-down menu.

  • Normal - the basic stopping conditions will be used.
  • At Range for Equal Speed - stop when the aircraft achieves the Range for Equal Speed.
  • At Range to Transition Speed - stop when the aircraft achieves the Range to Transition Speed.
  • After Target Current Procedure - stop after the target completes the procedure that it is performing when the aircraft rendezvous with it.
  • After Target Current Mission Phase - stop after the target completes the mission phase that it is performing when the aircraft rendezvous with it.
  • When Target Performance Mode Changes - stop when the target enters a new mode of flight (e.g., it transitions from forward flight to VTOL).
  • When Target Performance Phase Changes - stop when the target enters a new performance phase (e.g., it transitions from climbing to cruising).